backlight: ams369fg06: remove redundant variable 'before_power'

'before_power' was used to check the previous status when resume() is
called.  However, FB_BLANK_POWERDOWN was used in suspend() all the time,
so there is no need to check the previous status.  Also, redundant return
variables are removed to reduce the code.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>